Gas Mileage 2006 Infiniti G35

Let's dive deep into the gas mileage performance of the 2006 Infiniti G35. We're not just looking at the EPA numbers here; we're talking about real-world conditions, the factors that impact fuel economy, and how you can potentially improve it. This isn't just for the casual driver; it's geared towards the enthusiast who wants to understand their vehicle's inner workings and optimize its performance.

Understanding the Engine: The VQ35DE

The heart of the 2006 G35 is the venerable VQ35DE engine. This is a 3.5-liter (3498cc) naturally aspirated V6, known for its smooth power delivery and relatively robust design. Understanding its key features is crucial to understanding its fuel consumption. Here are a few key elements:

Displacement: As mentioned, 3.5 liters. Larger displacement engines generally consume more fuel, particularly under heavy acceleration.
Valve Train: The VQ35DE utilizes a Dual Overhead Camshaft (DOHC) configuration with four valves per cylinder (24 valves total). This allows for better airflow compared to single overhead cam designs, leading to improved power, but also potentially higher fuel consumption depending on tuning and driving style.
Variable Valve Timing (VVT): Nissan uses Continuously Variable Valve Timing Control System (CVTCS) on the intake camshafts. CVTCS optimizes valve timing based on engine speed and load, improving both power and fuel efficiency. Proper CVTCS function is critical for optimal mileage. Malfunctioning CVTCS solenoids or oil pressure issues can significantly impact fuel economy.
Fuel Injection: Multi-port fuel injection (MPFI) delivers fuel directly into each cylinder's intake port. This is generally more efficient than throttle-body injection, but less so than direct injection (which the VQ35DE does not have).
Compression Ratio: The compression ratio is around 10.3:1. This is relatively high for a naturally aspirated engine, contributing to power output, but also requiring higher octane fuel for optimal performance and preventing knocking (pre-ignition). Using lower octane fuel than recommended can lead to the ECU retarding timing, which negatively impacts both power and fuel economy.

Factory EPA Estimates vs. Real-World MPG

The EPA estimates for the 2006 G35 varied slightly depending on the model (sedan vs. coupe, manual vs. automatic). Generally, you're looking at something in the neighborhood of:

City: 18-20 mpg
Highway: 25-27 mpg
Combined: 21-23 mpg

However, these numbers are often optimistic. Real-world fuel economy can vary significantly based on several factors:

Driving Style: Aggressive acceleration, hard braking, and high-speed driving will drastically reduce fuel economy. The VQ35DE loves to rev, but doing so constantly will kill your MPG.
Traffic Conditions: Stop-and-go traffic is a fuel economy killer. Idling consumes fuel without covering any distance.
Maintenance: A poorly maintained engine will always be less efficient. Clogged air filters, worn spark plugs, and dirty fuel injectors can all contribute to poor gas mileage.
Tire Pressure: Underinflated tires increase rolling resistance, requiring the engine to work harder to maintain speed.
Vehicle Weight: Carrying unnecessary weight in the car reduces fuel economy.
Aftermarket Modifications: Certain modifications, such as larger wheels and tires, can negatively impact fuel economy. Performance modifications that increase horsepower often come at the expense of MPG.
Fuel Quality: Using lower-grade fuel than recommended can reduce fuel economy. While the engine can run on 87 octane, it's designed for 91 or higher.
Ethanol Content: Modern gasoline often contains ethanol (E10, E15). Ethanol has a lower energy density than gasoline, so fuel economy will be slightly reduced.

Common Issues Affecting Gas Mileage

Several specific issues can plague the 2006 G35 and negatively impact its fuel economy. These include:

Oxygen Sensors (O2 Sensors)

The G35 has multiple O2 sensors, including upstream (before the catalytic converters) and downstream (after the catalytic converters). These sensors measure the oxygen content in the exhaust and provide feedback to the ECU to adjust the air-fuel mixture. Faulty O2 sensors are a common cause of poor gas mileage. A failing sensor may provide inaccurate readings, causing the ECU to run the engine too rich (excess fuel) or too lean (insufficient fuel). You can diagnose O2 sensor problems with an OBD-II scanner that can read live data. Look for sluggish sensor responses or readings that are outside of the normal range.

Mass Airflow Sensor (MAF Sensor)

The MAF sensor measures the amount of air entering the engine. This information is crucial for the ECU to calculate the correct amount of fuel to inject. A dirty or faulty MAF sensor can provide inaccurate readings, leading to incorrect air-fuel mixtures and poor fuel economy. Cleaning the MAF sensor with a dedicated MAF sensor cleaner can often resolve the issue. Replace the sensor if cleaning doesn't help. Be careful when handling the sensor; the wire is delicate.

Fuel Injectors

Over time, fuel injectors can become clogged with deposits, affecting their spray pattern and fuel delivery. This can lead to uneven combustion and reduced fuel economy. Fuel injector cleaning additives can help, but severely clogged injectors may need to be professionally cleaned or replaced.

Spark Plugs

Worn or fouled spark plugs can cause misfires, which reduce fuel economy and can damage the catalytic converters. Inspect the spark plugs regularly and replace them according to the manufacturer's recommendations. Use the correct type of spark plug for your G35 (usually platinum or iridium).

Catalytic Converters

A clogged or failing catalytic converter restricts exhaust flow, reducing engine efficiency and fuel economy. Catalytic converter problems are often indicated by a "Check Engine" light and diagnostic trouble codes (DTCs) related to catalyst efficiency. Replacement can be expensive, so proper diagnosis is essential.

Exhaust Leaks

Leaks in the exhaust system before the oxygen sensors can skew the readings and cause the engine to run poorly, impacting fuel economy. Inspect the exhaust system for any signs of leaks, such as rust or black soot.

Brakes Dragging

Sticking brake calipers can cause the brakes to drag, increasing rolling resistance and reducing fuel economy. Check the brakes to ensure they are functioning properly and not binding.

DIY Maintenance and Tuning for Better MPG

Here are some steps you can take to improve the gas mileage of your 2006 Infiniti G35:

Regular Maintenance: Follow the manufacturer's recommended maintenance schedule, including oil changes, air filter replacements, spark plug replacements, and fuel filter replacements (if applicable).
Tire Pressure: Maintain proper tire pressure. Check the sticker on the driver's side door jamb for the recommended pressure.
Air Filter: Replace the air filter regularly. A clogged air filter restricts airflow, reducing engine efficiency.
MAF Sensor Cleaning: Clean the MAF sensor periodically with a dedicated MAF sensor cleaner.
Fuel Injector Cleaner: Use a fuel injector cleaner periodically to help keep the fuel injectors clean.
OBD-II Scanning: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs). Address any issues promptly.
Driving Habits: Practice fuel-efficient driving habits, such as avoiding aggressive acceleration and braking, and maintaining a steady speed.
Weight Reduction: Remove any unnecessary weight from the car.
ECU Tuning (with caution): A professional ECU tune can sometimes improve fuel economy, but it's crucial to choose a reputable tuner who understands the VQ35DE engine. A poorly executed tune can damage the engine. Be wary of "economy" tunes that promise unrealistic gains.
Consider Lightweight Wheels: While expensive, lightweight wheels can reduce unsprung weight, improving both acceleration and fuel economy.

Important Note: Modifying your vehicle can void warranties and may not be legal in all areas. Always check your local regulations before making any modifications.

Conclusion

The 2006 Infiniti G35 can deliver reasonable fuel economy, especially when properly maintained and driven responsibly. By understanding the factors that affect fuel mileage, addressing common issues, and performing regular maintenance, you can optimize the MPG of your G35 and enjoy its performance without breaking the bank at the gas pump. Remember to prioritize proper diagnosis before throwing parts at the problem, and always consult a qualified mechanic if you're unsure about any repair or modification. Happy driving!